Preheat oven to 350 F. Line and grease 2 9-inch cake pans with non-stick cooking spray. Set aside. In a large bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda and salt.
In another medium bowl, whisk together eggs, milk, coffee, vegetable oil and vanilla extract. Using either a hand or stand mixer, beat wet ingredients into the dry ingredients. Beat until smooth.
Evenly divide cake batter between the two prepared cake pans. Bake for 35 minutes. Let cool completely.
In a large bowl, using either a hand or stand mixer, beat softened butter with powdered sugar and cocoa powder until smooth. Add in milk and vanilla extract. Beat until smooth, adding in more milk as needed to thin.
Layer cooled chocolate cake and frost each layer. Frost entire cake and sprinkle with crushed oreo cookies. Decorate cake with gummy worms.
